Sheet gripping device



June 3, 1969 P. REINHARDT 3,447,800

SHEET GRIPPING DEVICE Filed July 14, 1967 4o 38 42- 4| WE PETER REIYNH R T United States Patent 3,447,800 SHEET GRIPPING DEVICE Peter Reinhardt, Leipzig, Germany, assignor to VEB Druckmaschinenwerk Planeta, Radebeul, Germany Filed July 14, 1967, Ser. No. 653,539 Int. Cl. B65h 5/06, 29/06 US. Cl. 271-51 6 Claims ABSTRACT OF THE DISCLOSURE Background of the invention The present invention relates to sheet gripping devices for sheet printing and handling machines. A plurality of gripping fingers is normally arranged on the gripper carriage, gripper bars or cylinders of printing machines and are pressed against a gripper contact or backing element with a sheet held therebetween for the purpose of transferring the sheet to or from the printing operation. The sheet must be held securely without slipping or sliding so that alignment is maintained; adequate pressure must be applied to the grippers to hold the sheet frictionally. This grip may be enhanced by use of friction coatings on the gripper finger and backing surfaces.

Conventional practice requires that the sheets be perfectly aligned before the grippers are closed; once the grippers securely engage the sheets, no further adjustment in sheet position can occur, and imperfectly aligned sheets will result in misprinting and waste. Perfect alignment has heretofore involved either the sheets being brought to a stop and aligned before being gripped; or the sheets being conveyed at substantial distance or a considerably reduced speed to permit alignment before being gripped. These alternatives both result in severe limitation of the capacity or output of the machine; stopping and then reaccelerating the sheets to the relatively high speeds usually employed for sheet transfer represents a bottleneck to rapid efiicient production; fully aligning the sheets while in motion and before gripping involves an undesirably long conveyor and consequent space waste.

In addition, no feasible method has been heretofore devised for sheet alignment after the grippers have taken hold; in the prior art, such adjustment would require shifting of the entire gripping arrangement, involving intricate and expensive mechanisms.

Summary of the invention The present invention provides a sheet gripping device which overcomes the problems of the prior art by permitting alignment of the sheet after the grippers have grasped the sheet without requiring any shifting of the gripping device itself.

More specifically, according to the invention, both the gripper fingers and the gripper counter or backing elements are provided with additional elements which, while holding the sheet securely and unshiftably with respect to the direction of travel, permit a movement of the sheet generally at a right angle to the direction of sheet and gripper trabel. These additional elements may preferably and advantageously be cylindrical rollers, mounted for free rotation in both the gripper fingers and the backing 3,447,800 Patented June 3, 1969 elements. Such rollers are oriented so that their axes of rotation are in line with the travel path of the sheet and grippers and at right angles to the direction of sheet alignment. When the gripper is in operatively closed position, the roller mounted in each finger and the roller mounted in each corresponding counter backing are parallely disposed one above the other, firmly holding the sheet therebetween in linear contact. In this position and while being conveyed, the sheet may be contacted by guide elements on the machine and thereby be shifted laterally into precise alignment, i.e. at right angles to the line of travel,

this motion being permitted by rotation of the rollers.

The cylindrical rollers may be mounted conveniently on the gripper elements so that more than one-half the body of each roller is held within the profile of the gripper finger or backing. In this way, the rollers are prevented from falling out when the gripper elements are open. In order to provide for free rotation of the rollers, the roller bearing surfaces may be treated. Also, since normal lubrication of the rollers is prohibited by the potential damage to the sheets by staining, it may be useful to introduce compressed air into each of the gripper elements as a support and lubricant for the rollers.

In place of cylindrical rollers, resilient see-saw-type or blade-type elements arranged in the gripper parts may be employed to hold the sheet in linear contact while permitting transverse positioning of the sheet.

If sensitive sheet material requires more surface contact than the linear contact provided by rollers to avoid excessive stress on the sheet, various substitute elements may replace one or both of the gripping rollers.

Thus, normally on a sheet handling machine, two or more sheet gripper fingers are used for holding and conveying each sheet. These gripping fingers are mounted on a gripper shaft and operated in unison. The gripper backing element is usually in the form of a backing rail which is screwed on the gripper carriage or the gripper cylinder. According to the present invention, the gripper fingers may, for example, be provided with cylindrical rollers in the above-described manner, while the backing rail, held fixedly with respect to the direction of travel, may be slightly displaceable transversely, so that sheet position adjustment at right angles to travel may be achieved. With this combination, linear contact between gripper finger roller and sheet occurs, while broader surface contact between sheet and backing rail reduces the stress to which the sheet might be subjected. In this case, no relative movement occurs between the sheet and the backing rail;

the backing rail is moved together with the sheet when the sheet is guided into alignment. The backing rail may be provided with retracting means, such as tension or compression springs, to return it to an end position opposite the direction of alignment when the sheet has been released and the gripper is open.

Broad surface contact between the sheet and each gripper element may be provided by a gripping shoe mounted on each gripper finger or each gripper backing element in place of a roller. These gripping shoes are aflixed to gripper elements so that no movement in the direction of conveyor travel is permitted, while limited arranged in the gripper elements with pins, balls or rollers between shoe and gripper element body, thus providing easy displacement of the shoes; and such intermediate bearings may be readily lubricated without the danger of soiling the sheets.

Brief description of the drawings Several preferred embodiments illustrative of the present invention will be fully described in clear concise terms with the heip of the accompanying drawing, in which:

FIG. 1 is a schematic side elevational view of a sheet gripping device in its closed position, employing cylindrical rollers as the means for adjusting the alignment of the sheet;

FIG. 2 is a sectional view of the device taken along line 22 of FIG. 1;

FIG. 3 is a longitudinal sectional view of a second embodiment of the device, in which the gripper shoes are employed in place of the rollers of the first embodiment of FIGS. 1 and 2;

FIG. 4 is a longitudinal sectional view of still another embodiment of the invention, showing an arrangement on a cylinder, in which a roller in the gripper finger is illustrated in cooperative relationship with a transversely displaceable backing rail mounted on the cylinder; and

FIG. 5 is a section taken along line 55 of FIG. 4.

Description of a preferred embodiment As illustrated in FIGS. 1 and 2, the first embodiment provides a gripper finger 1 and a gripper backing element 3, with a sheet 2 held therebetween. Sheet 2 is to be aligned in a direction at right angles to the direction of travel indicated by arrow T in FIG. 1. A cylindrical roller 4 is disposed in gripper finger 1 in such a way that roller 4 is rotatably maintained in finger 1. Similarly, a roller 5 is supported in gripper backing element 3. The axes of rollers 4 and 5 extend in the direction of travel T. It is evident that sheet 2, while rigidly secured and immoveable in direction T, may be moved as the rollers 4 and 5 rotate in the transverse direction of alignment, indicated by arrow A in FIG. 2. Rollers 4 and 5 are arranged respectively in gripper finger 1 and gripper backing 3 each with more than half of its bulk disposed within the profile of its respective carrier element; the deformation of each carrier element to reduce the roller opening to a size smaller than the roller diameter prevents each roller from dropping out when not engaged in gripping.

In the embodiment of FIG. 3, gripper finger 21 and gripper backing element 23 are provided respectively with laterally-extending support-like gripper shoes 27 and 29, each shoe fixedly attached in the direction of travel T, but readily displaceable in the direction of alignment. In FIG. 3, the direction of alignment extends vertically with respect to the plan of the drawing. To facilitate easy movement of the gripper shoes 27 ad 20, hearing rollers 26 and 28 are provided. In other words, hearing roller 26 is interposed between gripper finger 21 and its shoe 27; and bearing roller 28 is interposed between gripper backing 23 and its shoe 29. Sheet 22 is held in full surface contact between the gripper shoes 27 and 29. When gripper finger 21 releases sheet 22, gripper shoes 27 and 29 may be returned to their original end position opposite to the direction of alignment by means of springs (not shown) so that for each alignment action, the entire moveable range of adjustment provided for shoes 27 and 29 is available.

In the embodiment of FIGS. 4 and 5, gripper finger 31 carries a roller 34, a combination identical to finger 1 and roller 4 of FIG. 1 and described above. Gripper cylinder 41 is provided with a backing rail 41} which serves as common backing for all the gripper fingers 31 present. Backing rail 40 is held by a supporting Strip 42 and is mounted on bearing pins 38 so that said backing rail 40 is displaceablc along the direction of alignment A at right angle to direction of sheet travel T. Sheet 32 is clamped between roller 34 and backing rail 40, is held securely in the direction of sheet travel T. Alignment of sheet 32 may be accomplished by the controlled displacement of backing rail 40, or by guide means on the machine (not shown) which contact sheet 32 directly; in both instances, roller 34 rotates neutrally to permit sheet 32 accompanied by backing rail 40 to move laterally.

Various combinations of the means for gripping and laterally aligning the sheets may be employed on gripper fingers and backing members to meet specific requirements of sheet character and machine structure. Thus rollers, gripping shoes, resiliently supported see-saw-type or bladetype devices may be arranged in any desired combination on the gripper fingers, the gripper backing members, or both. Similarly, any of these gripping elements mounted on the gripper fingers may be used to cooperate with a transversely displaceable backing rail. All of the abovedescribed sheet gripping devices are fully effective on sloping conveyor runs with the gripping-aligning elements adjusted or guided inclined to the desired angular degree.

The preferred embodiments of the invention have been illustrated and described. Various modifications and changes may be made without departing from the invention as described in the claims.

What is claimed is:

1. In a sheet processing machine, a sheet gripping device comprising a plurality of gripper fingers; at least one gripper backing member, cooperating with said gripper fingers to hold a sheet therebetween; and in each of said gripper fingers and said gripper backing member, means for holding the sheet fixedly in the direction of sheet travel and movably in a direction substantially at a right angle to the direction of sheet travel; whereby said gripping device in its operatively closed position permits lateral alignment of the sheet which is being conveyed, wherein said holding means in each said gripper finger comprises a gripper shoe mounted on said gripper finger fixedly in the direction of sheet travel and moveably in a transverse direction substantially at a right angle to the direction of sheet travel.

2. The sheet gripping device according to claim 1 wherein said holding means in each said gripper finger comprises at least one roller in said gripper finger mounted for free rotation on an axis which coincides with the direction of sheet travel.

3. The sheet gripping device according to claim 1, wherein said holding means in said gripper backing member comprises at least one roller in said gripper backing member mounted for free rotation on an axis which coincides with the direction of sheet travel.

4. The sheet gripping device according to claim 1, wherein an intermediate rolling means is positioned between said gripper shoes and said gripper fingers for permitting slidable movement of said gripper shoes in said transverse direction substantially at a right angle to the direction of sheet travel.

5. In a sheet processing machine, a sheet gripping device comprising a plurality of gripper fingers; at least one gripper backing member, cooperating with said gripper fingers to hold a sheet therebetween; and in each of said gripper fingers and said gripper-backing member, means for holding the sheet fixedly in the direction of sheet travel and movably in a direction substantially at a right angle to the direction of sheet travel; whereby said gripping device in its operatively closed position permits lateral alignment of the sheet which is being conveyed, wherein said holding means in said gripper backing member comprises a gripper shoe mounted on said gripper backing member fixedly in the direction of sheet travel and moveably in a transverse direction substantially at a right angle to the direction of sheet travel.

6. In a sheet processing machine, a sheet gripping device comprising a plurality of gripper fingers; at least one gripper backing member, cooperating with said gripper fingers to hold a sheet therebetween; and in each of said gripper fingers and said gripper backing member, means for holding the sheet fixedly in the direction of sheet travel and movably in a direction substantially at a 5 I 6 right angle to the direction of sheet travel; whereby said FOREIGN PATENTS gripping device in its operatively closed position permits lateral alignment of the sheet which is being conveyed, 943649 5/1956 Germany wherein said gripper means backing member comprises RICHARD H AEGERTER, primary Emmi-"en a single common backing rail cooperating with all said 5 gripper fingers; and wherein said holding means comprises U S L XR. said common backing rail mounted fixedly in the direction 271 32 of sheet travel and moveably in a transverse direction substantially at a right angle to the direction of sheet travel. 10 

